I keep reading about the spam problem. Can't confirm that for me. I extremely rarely get spam in my inbox while on gmail I got about the same amounts but also quite a few false positives.
The mobile client: I don't know the iOS client but urgh. The Android FM client is pretty lame :D Luckily, I rarely use it.
I use next cloud for all docs, images, etc. and neither has an integration so that's a toss-up for me ;)